The present invention relates to a displacement type fluid machine, which is used for a cooling medium compressor of the type used in a refrigerator, a freezer, an air conditioner, etc., a gas compressor, such as an air compressor, a vacuum pump, a helium compressor, etc., an expander, a fluid pump, and so forth.
Conventional techniques in the application of a displacement type fluid machine will be explained with reference to a scroll compressor, as an example. In a scroll compressor as disclosed in Japanese Patent Application Laid-Open Hei 6-81792, oil is fed to sliding portions, such as bearings, by a pump including a spiral groove provided near an oil tank situated in the compressor. Further, in scroll compressors disclosed in Japanese Patent Applications Laid-Open Hei 8-303364 and Hei 9-32760, oil is fed to sliding portions by a displacement type pump and a centrifugal pump, respectively, using centrifugal force generated by rotation of a shaft.
In all of the above conventional techniques, oil is fed to sliding portions, such as bearings, by one oil-feed pump provided near an oil-storing chamber. Accordingly, it is necessary to determine the capacity of that oil-feed pump so that the oil-feed pump is capable of feeding oil in an amount which satisfies the needs of a plurality of bearings situated in a fluid machine; however, this frequently results in the need for an oil-feed pump having an excessive oil-feed capacity. Thus, there has been a problem in that the oil-feeding becomes excessive during high-speed operation of the compressor, and so the performance of the compressor is degraded by an increase in the power consumed to compress the excess oil.
Further, since the oil-feed pump itself can cause a large power loss, the oil-feed pump increases the total mechanical power loss, and this has been a cause of the degrading of the performance of the compressor.
The present invention has been achieved in order to solve the above problems, and it is an object of this invention to provide a displacement type fluid machine which is capable of reducing mechanical power loss by preventing excessive oil-feeding during high speed operation of the fluid machine.
To achieve the above object, the present invention provides a displacement type fluid machine, wherein a lubricating fluid pump for transferring lubricating oil to lubricate each bearing is provided at each sliding portion by forming a pump at or near each bearing for rotatably supporting a shaft of the fluid machine, the lubricating fluid pump being a non-displacement type pump.
By the above composition of the bearings and the pumps, lubricating oil can be fed to each bearing by the pump provided at that bearing in a quantity necessary for lubricating each bearing. Therefore, each pump has only to provide a capacity such that the pump head to the next pump can be ensured. Thus, while nearly ideal bearing oil-feeding characteristics can be implemented, the power loss of each pump can be greatly reduced.
Meanwhile, there are two types of pumps, that is, a displacement type pump which transfers fluid by compartmentalizing the fluid into respective volumes and pressurizing the compartmentalized fluid, and a non-displacement type pump, such as a centrifugal pump, a viscous pump, etc., which continuously transfers fluid without compartmentalizing the fluid into respective volumes.